1. Field of the Invention
This invention relates to an apparatus for tapering sheets of foam insulation. More particularly, this invention relates to an apparatus for tapering sheets of foam insulation which utilizes a rotating wire heated above the melting temperature of the foam insulation to remove a section of insulation from the sheet. The heated wire maintains a generally uniform temperature across the section of the wire in contact with the insulation to evenly melt and cut the foam insulation at the desired angle as the insulation is forced across the wire.
2. Summary of Related Art
The roofing process for flat roof applications requires the placement of sheets of foam insulation onto the roof prior to applying the sealing materials. The insulation must be sloped in the appropriate manner so that the water drains correctly. Therefore, the sheets of insulation must be tapered horizontally to obtain the appropriate pitch in the roof. The sheets of insulation must be cut to create this horizontal slope.
The known tapering equipment currently in use provides a heated wire which is maintained in a taut condition as the insulation is continuously forced against the wire. The heat from the wire melts the insulation in the desired cutting path. The process is limited by the speed at which the insulation can be forced around the heated wire. The melting process is preferred over a cutting process because of the difficulty in cutting the insulation to form a smooth surface.
One of the problems which frequently occurs with tapering equipment is that the heated wire has the tendency to break. The speed of the tapering process is increased by using a high temperature wire with more force in driving the insulation across the heated wire. The heat dissipation along the length of the wire is uneven, with the wire being hotter at the edges of the insulation and cooler at the center portion of the insulation. The breakage typically occurs at the middle of the wire strand. The cooler middle wire segment cannot melt the insulation as fast as the hotter end segments. As force is applied to move the insulation, tension in the slower melting center segment builds up until the wire breaks.
The breakage and subsequent replacement of the wire on the tapering equipment can create a significant amount of downtime, which results in an ineffective use of the tapering equipment and additional costs for a roofing project.
Another problem which can occur in using a heated wire to taper the sheet of insulation is that the wire reaches a temperature that will burn the insulation. Because of the problems with burning insulation, the possibility of increasing the production rate for tapering the sheet of insulation by raising the temperature of the wire is limited. The temperature limitations using a heated wire to melt the insulation results in a very slow process for tapering the sheets of insulation.
U.S. Pat. No. 4,536,145 to Sawyer, et. al. discloses an apparatus for cutting a contoured surface in the face of a polystyrene foam block. The apparatus utilizes a heated wire to cut through the foam block. The wire is static and therefore subject to uneven heating and subsequent breakage.
U.S. Pat. No. 4,779,497 to Lee shows an apparatus for removing excess masking film from the outer periphery of a silicon wafer. The apparatus continuously feeds a heated wire and an unheated wire which contact the excess masking film and trims it from the silicon wafer. The invention utilizes a rotating table that holds the silicon wafer and moves it into the wires. The thin film is first cut by the heated wire and then trimmed off by the unheated wire.
U.S. Pat. No. 4,850,844 to Hunting discloses an apparatus for tapering plastic shingles. The apparatus utilizes at least one heated wire that is transversely mounted across the path of a moving shingle. The wire is static with one end adjustable to vary the angle of the cut across the shingle.
In the roofing industry, there is a need for a faster and more efficient means for tapering sheets of insulation. Another concern in the tapering equipment is to reduce the time and expense of wire replacement, which could be addressed by a wire with an extended life.